The present invention relates to an electric circuit for a camera, and, more particularly, to an electric circuit for a camera which is invulnerable to the influence of a change in environment, such as temperature.
Recently, the electric circuit for a camera uses various components. Due to the following reasons, there is a growing demand that the influence of the temperature on sensors, actuators and a display unit, which are included in a camera, should be reduced as much as possible.
For example, if the focusing/light measuring properties of sensors have a temperature dependency, insufficient exposure and out-of-focusing occur at a low temperature. Unless the outputs of the actuators are controlled properly, out-of-focusing of the lens, a variation between frames of a film and a mis-selection of gears would occur and the mechanisms may be damaged or malfunction in some cases. Further, the display unit, particularly, an LCD display unit, suffers from insufficient light display at a low temperature and is likely to have crosstalking at a high temperature.
Many of recent cameras have a D/A converter built in a one-chip microcomputer.
For example, Jpn. Pat. Appln. KOKAI Publication No. 9-258606 filed earlier by the assignee of the present application describes a scheme of detecting a blur using a blur sensor and a CPU which incorporates a D/A converter.
Jpn. Pat. Appln. KOKAI Publication No. 58-27004 describes the technique that provides the reference voltage of an A/D converter with a temperature characteristic to compensate for the temperature of a compression diode for AF.
Further, Jpn. Pat. Appln. KOKAI Publication No. 5-61443 discloses the technique that uses a CPU for display compensation.
Although the aforementioned Jpn. Pat. Appln. KOKAI Publication No. 9-258606 describes the technique of processing a blur with a CPU equipped with a D/A converter, it fails to describe compensation for a temperature dependency.
While the technique described in the aforementioned Jpn. Pat. Appln. KOKAI Publication No. 58-27004 corrects the temperature of the compression diode for AF, the correction is done at the time of A/D conversion and analog-based correction is not possible so that delicate signals cannot be corrected sufficiently. Although the aforementioned Jpn. Pat. Appln. KOKAI Publication No. 5-61443 uses a CPU for display compensation, it is not a D/A converter in a one-chip microcomputer so that the circuit is complicated, making it difficult to carry out various compensations with a simple structure.